HEADACHE – DIAGNOSTIC APPROACH

History: most information is derived from determining:

The following table classifies causes in these categories:

(*) Indicates that attacks can be recurrent

HEADACHE – SPECIFIC CAUSES

TENSION TYPE HEADACHE

This is the commonest form of headache experienced by 70% of males and 90% of females at some time in their lives.

Characteristics: Diffuse, dull, aching, ‘band-like’ headache, worse on touching the scalp and aggravated by noise; associated with ‘tension’ but not with other physical symptoms. Attacks may be chronic or episodic. Depression commonly co-exists.

Duration: Many hours–days.

Frequency: Infrequent or daily; worse towards the end of the day. May persist over many years.

Mechanism: ‘Muscular’ due to persistent contraction, e.g. clenching teeth, head posture, furrowing of brow. Some overlap with transformed migraine (see below).

Treatment: Reassurance. Attempt to reduce psychological stress and analgesic over-use (see medication-overuse headache). Amitriptyline and other tricyclic antidepressants or β-blockers.

MIGRAINE

Migraine is a common, often familial disorder characterised by unilateral throbbing headache.

Onset: Childhood or early adult life.

Incidence: Affects 5–10% of the population.

Female:male ratio: 2:1

Family history: Obtained in 70% of all sufferers.

Two recognisable forms exist:

Specific diagnostic criteria are required for migraine with and without aura.

The aura is absent. The headache has similar features, but it is often poorly localised and its description may merge with that of ‘tension’ headache.

The aura of migraine may take many forms. The visual forms comprise: flashing lights, zig-zags (fortifications), scintillating scotoma (central vision) and may precede visual field defects. Such auras are of visual (occipital) cortex origin.

The headache is recurrent, lasting from 2 to 48 hours and rarely occurring more frequently than twice weekly. In migraine equivalents the aura occurs without ensuing headache.

Specific types of migraine with aura

Basilar: Characterised by bilateral visual symptoms, unsteadiness, dysarthria, vertigo, limb paraesthesia, even tetraparesis. Loss of consciousness may ensue and precede the onset of headache. This form of migraine affects young women.

Hemiplegic: Characterised by an aura of unilateral paralysis (hemiplegia) which unusually persist for some days after the headache has settled. Often misdiagnosed as a ‘stroke’. When familial, mendelian dominant inheritance is noted. Recovery is the rule.

Retinal

Unilateral (monocular) visual loss which is reversible and followed by headache. Ophthalmological examination between episodes is normal.

Precipitating factors in migraine

– Dietary: alcohol, chocolate and cheese (contain tyramine).

– Hormonal: often premenstrual or related to oral contraceptive (fluctuations in oestrogen).

– Stress, physical fatigue, exercise, sleep deprivation and minor head trauma.

Diagnosis

Clinical history with	– occasional positive family history – travel sickness or migraine variants (abdominal pains) in childhood – onset in childhood, adolescence, early adult life or menopause
Distinguish	– partial (focal) epilepsy (in hemiplegic or hemisensory migraine) – transient ischaemic attack (in hemiplegic or hemisensory migraine) – arteriovenous malformation – gives well localised but chronic headache) – hypoglycaemia

Management

(i) Identification and avoidance of precipitating factors

(ii) Treatment of acute attacks:

Simple analgesics (e.g. aspirin) with metoclopramide to enhance reduced absorption during an attack. If vomiting is prominent anti-emetic (domperidone or prochlorperazine) and analgesic can be helpful.

Sumatriptan (a selective 5HT₁ agonist) and other triptans e.g. Naratriptan, Rizatriptan and Zolmitriptan – effectively reverse dilatation in extracranial vessels. Given orally or subcutaneously.

Ergotamine – widespread action on 5HT receptors reversing dilatation. Give orally or by inhalation, injection or by suppository.

Methylprednisolone i.m. or i.v. will halt the attack when prolonged (status migrainosus).

(iii) Prophylaxis: use only for frequent and severe attacks

Pizotifen (5HT₂ receptor blocker)

Propranolol (beta adrenergic receptor blocker)

Calcium antagonists (verapamil), antidepressants(amitriptyline) and anticonvulsants, (topiramate or sodium valproate).

Medication Overuse Headaches

Some patients with episodic tension headache or migraine find their headache pattern changes so that they have headaches most days. Many such patients take regular analgesics and/or triptans and this overuse (>14 days a month) can cause medication overuse headaches (MOH). These do not respond to prophylactic agents and will improve on stopping the regular analgesics; this can take some weeks and headaches can be worse in the short-term.

POST-TRAUMATIC HEADACHE

A ‘common migraine’ or ‘tension-like’ headache may arise after head injury and accompany other symptoms including light-headedness, irritability, difficulty in concentration and in coping with work. This will often respond to amitriptyline or migraine prophylaxis.

CLUSTER HEADACHES (Histamine cephalgia or migrainous neuralgia)

‘Cluster headaches occur less frequently than migraine, and more often in men, with onset in middle age. Charecterised by episodes of severe unilateral pain, lasting 10 minutes to 2 hours, around one eye, associated with conjunctival injection, lacrimation, rhinorrhea and occasionally a transient Horner’s syndrome. The episodes occur between once and many times per day, often wakening from sleep at night. ‘Clusters’ of attacks separated by weeks or even many months. Alcohol may precipitate the attacks.’

Other Trigeminal Autonomic Cephalagias

Cluster headache is the most common form of trigeminal autonomic cephalalgia, where there is a combination of facial pain and autonomic dysfunction. Other rarer combinations of facial pain and antonomic symptoms include:

Hemicrania continua: continuous unilateral moderately severe head pain with exacerbations and variable tearing and partial Horner’s syndrome. More common in women than men (3:1). Responds dramatically to indometacin.

Paroxysmal hemicrania: Same pain but lasts 2-45 minutes multiple times a day. Responds to indometacin.

Short-lasting Unilateral Neuralgiform pain with Conjunctival injection and Tearing (SUNCT): brief pain lasting seconds to 3 minutes with associations described in its name. Women:men, 2:1. Does not respond to indometacin. Lamotrigine has some effect.

GIANT CELL (TEMPORAL) ARTERITIS

Giant cell arteritis, an autoimmune disease of unknown cause, presents with throbbing headache in patients over 60 often with general malaise. The involved vessel, usually the superficial temporal artery, may be tender, thickened, and but nonpulsatile.

Neurological symptoms: strokes, hearing loss, myelopathy and neuropathy.

Jaw claudication: pain when chewing or talking due to ischaemia of the masseter muscles is pathognomonic.

Visual symptoms are common with blindness (transient or permanent) or diplopia.

Associated systemic symptoms – weight loss, lassitude and generalised muscle aches – polymyalgia rheumatica in one-fifth of cases.

Duration: the headache is intractable, lasting until treated.

Mechanism:

Large and medium-sized arteries undergo intense ‘giant cell’ infiltration, with fragmentation of the lamina and narrowing of the lumen, resulting in distal ischaemia as well as stimulating pain sensitive fibres. Occlusion of important end arteries, e.g. the ophthalmic artery, may result in blindness; occlusion of the basilar artery may cause brain stem or bilateral occipital infarction.

Diagnosis: ESR usually high. Blood film shows anaemia or thrombocytosis. C-reactive protein and hepatic alkaline phosphatase elevated. Biopsy of 1 cm length of temporal artery is often diagnostic.

Treatment: Urgent treatment, prednisolone 60 mg daily, prevents visual loss or brain-stem stroke, as well as relieving the headache. If complications have already occurred e.g. blindness, give parenteral high dose steroids. Monitoring the ESR allows gradual reduction in steroid dosage over several weeks to a maintenance level, e.g. 5 mg daily. Most patients eventually come off steroids; 25% require long-term treatment and if so, complications commonly occur.

HEADACHE FROM RAISED INTRACRANIAL PRESSURE

HEADACHE DUE TO INTRACRANIAL HAEMORRHAGE

Characteristics:

Associated features:

Management: further investigation – CT scan/lumbar puncture (see Meningism, page 75).

N.B. Consider sudden severe headaches to be due to subarachnoid haemorrhage until proved otherwise.

NON-NEUROLOGICAL CAUSES OF HEADACHE

Local causes:

Sinuses: Well localised. Worse in morning. Affected by posture, e.g. bending.

X-ray – sinus opacified. Treatment – decongestants or drainage.

Ocular: Refraction errors may result in ‘muscle contraction’ headaches

– resolves when corrected with glasses.

Acute glaucoma can produce headache but is accompanied by other symptoms, e.g. misting of vision, ‘haloes’.

Dental disease: Discomfort localised to teeth. Check for malocclusion.

Check temporomandibular joints.

Systemic causes:

Headache may accompany any febrile illness or may be the presenting feature of accelerated hypertension or metabolic disease, e.g. hypoglycaemia, hypercalcaemia.

Many drugs produce headache

CEREBROSPINAL FLUID (CSF)

Secreted at a rate of 500 ml per day from the choroid plexus, CSF flows through the ventricular system and enters the subarachnoid space via the 4th ventricular foramina of Magendie and Luschka.

Under normal conditions, CSF flows freely through the subarachnoid space and is absorbed into the venous system through the arachnoid villi. If flow is obstructed at any point in the pathway, hydrocephalus with an associated rise in intracranial pressure develops, as a result of continued CSF production. With an expanding intracranial mass lesion, normal pressure is initially maintained by CSF expulsion to the expandable lumbar theca. Further expansion and subsequent brain shift may obstruct the free flow of CSF not only to the lumbar theca but also to the arachnoid villi, causing an acute rise in intracranial pressure.

BRAIN WATER/OEDEMA

Cerebral oedema – an excess of brain water – may develop around an intrinsic lesion within the brain tissue, e.g. tumour or abscess or in relation to traumatic or ischaemic brain damage, and contribute to the space-occupying effect.

Different forms of cerebral oedema exist:

Vasogenic: excess fluid (protein rich) passes through damaged vessel walls to the extracellular space – especially in the white matter. The extracellular fluid gradually infiltrates throughout normal brain tissue towards the ventricular CSF and this drainage route may aid clearance. e.g. adjacent to tumour.

Cytotoxic: fluid accumulates within cells – neurons and glia i.e. intracellular, e.g. toxic or metabolic states.

Interstitial: when obstructive hydrocephalus develops, CSF is forced through to the extracellular space especially in the periventricular white matter.

With ischaemic damage, as cell metabolism fails, intracellular Na⁺ and Ca²⁺ increase and the cells swell i.e. cytotoxic oedema. Capillary damage follows and vasogenic oedema supervenes.

CEREBRAL BLOOD FLOW (CBF)/CEREBRAL BLOOD VOLUME (CBV)

Blood flow is dependent on blood pressure and the vascular resistance:

Inside the skull, intracranial pressure must be taken into account:

Under normal conditions the cerebral blood flow is coupled to the energy requirements of brain tissue. Various regulatory mechanisms acting on the arterioles maintain a cerebral blood flow sufficient to meet the metabolic demands.

FACTORS AFFECTING THE CEREBRAL VASCULATURE

Autoregulation

– A change in the cerebral perfusion pressure results in a compensatory change in vessel calibre.

Any change in blood vessel diameter results in considerable variation in cerebral blood volume and this, in turn, directly affects intracranial pressure.

Energy requirements differ in different parts of the brain. To meet such needs in the white matter, flow is 20 ml/100 g/min, whereas in the grey matter flow is as high as 100ml/100g/min.

Autoregulation is a compensatory mechanism which permits fluctuation in the cerebral perfusion pressure within certain limits without significantly altering cerebral blood flow.

A drop in cerebral perfusion pressure produces vasodilation (probably due to a direct ‘myogenic’ effect on the vascular smooth muscle) thereby maintaining flow; a rise in the cerebral perfusion pressure causes vasoconstriction.

Neurogenic influences appear to have little direct effect on the cerebral vessels but they may alter the range of pressure changes over which autoregulation acts.

Autoregulation fails when the cerebral perfusion pressure falls below 60 mmHg or rises above 160 mmHg. At these extremes, cerebral blood flow is more directly related to the perfusion pressure.

In damaged brain (e.g. after head injury or subarachnoid haemorrhage), autoregulation is impaired; a drop in cerebral perfusion pressure is more likely to reduce cerebral blood flow and cause ischaemia. Conversely, a high cerebral perfusion may increase the cerebral blood flow, break down the blood–brain barrier and produce cerebral oedema as in hypertensive encephalopathy.

INTRACRANIAL PRESSURE (ICP)

Intracranial pressure, measured relative to the foramen of Monro, under normal conditions ranges from 0–135 mm CSF (0–10 mmHg) although very high pressure, e.g. 1000 mm CSF may occur transiently during coughing or straining.

When intracranial pressure is monitored with a ventricular catheter, regular waves due to pulse and respiratory effects are recorded (page 53). As an intracranial mass expands and as the compensatory reserves diminish, transient pressure elevations (pressure waves) are superimposed. These become more frequent and more prominent as the mean pressure rises.

Eventually the rise in intracranial pressure and resultant fall in cerebral perfusion pressure reach a critical level and a significant reduction in cerebral blood flow occurs. Electrical activity in the cortex fails at flow rates about 20 ml/100 g/min. If autoregulation is already impaired these effects develop even earlier. When intracranial pressure reaches the mean arterial blood pressure, cerebral blood flow ceases.

INTERRELATIONSHIPS

Many factors affect intracranial pressure and these should not be considered in isolation. Inter-relationships are complex and feedback pathways may merely serve to compound the brain damage.

CLINICAL EFFECTS OF RAISED INTRACRANIAL PRESSURE

A raised ICP will produce symptoms and signs but does not cause neuronal damage provided cerebral blood flow is maintained. Damage does, however, result from brain shift – tentorial or tonsillar herniation.

Clinical features due to ↑ICP:

BRAIN SHIFT – TYPES

Unchecked lateral tentorial herniation leads to central tentorial and tonsillar herniation, associated with progressive brain stem dysfunction from midbrain to medulla.

CLINICAL EFFECTS OF BRAIN SHIFT

An injudicious lumbar puncture in the presence of a subtentorial mass may create a pressure gradient sufficient to induce tonsillar herniation.

N.B. Harvey Cushing described cardiovascular changes – an increase in blood pressure and a fall in pulse rate, associated with an expanding intracranial mass, and probably resulting from direct medullary compression. The clinical value of these observations is often overemphasised. They are often absent; when present they are invariably preceded by a deterioration in conscious level.

INVESTIGATIONS

Patients with suspected raised intracranial pressure require an urgent CT/MRI scan. Intracranial pressure monitoring where appropriate (see page 53).

TREATMENT OF RAISED INTRACRANIAL PRESSURE

When a rising intracranial pressure is caused by an expanding mass, or is compounded by respiratory problems, treatment is clear-cut; the mass must be removed and blood gases restored to normal levels – by ventilation if necessary.

In some patients, despite the above measures, cerebral swelling may produce a marked increase in intracranial pressure. This may follow removal of a tumour or haematoma or may complicate a diffuse head injury. Artificial methods of lowering intracranial pressure may prevent brain damage and death from brain shift, but some methods lead to reduced cerebral blood flow, which in itself may cause brain damage (see page 84).

Intracranial pressure is monitored with a ventricular catheter or surface pressure recording device (see page 52). Treatment may be instituted when the mean ICP is > 25 mmHg. Ensure cause is not due to constriction of neck veins.